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1. Advantages of RFID in Sales in the Logistics Industry For the logistics industry, enterprises and customers are most concerned about the speed of transportation and the accuracy of information. RFID can precisely meet these conditions. In the logistics industry application, it has the following advantages:
(1) Read and write quickly. Only one barcode can be scanned at a time, and the RFID reader can recognize and read several RFID tags at the same time.
(2) Reading and writing distance is far away. When covered, RFID can penetrate non-metallic or non-transparent materials such as paper, wood, and plastic, and is capable of penetrating communication. The bar code scanner must be able to read the bar code at close range without object obstruction.
(3) Can be reused. Now that barcodes cannot be changed after printing, RFID tags can be added, modified, or deleted repeatedly.
(4) The chip itself can store information. The capacity of one-dimensional bar code is 50 bytes, the maximum capacity of two-dimensional bar code can store 2 to 3,000 characters, and the maximum capacity of RFID is several megabytes. With the development of memory carriers, the data capacity also has a tendency of expanding. In the future, the amount of data that an item needs to carry will become larger and larger, and the demand for capacity expansion of a label will increase correspondingly.
(5) Pollution resistance and durability. The carrier of traditional bar code is paper, so it is easily contaminated, but RFID has strong corrosion resistance to water, oil, chemicals and other substances. In addition, bar codes are attached to plastic bags or outer carton boxes, so they are particularly vulnerable to breakage; RFID tags are used to store data in the chip and are therefore protected from contamination.
2. System Design 2.1 System Design Principles The sales system of the logistics industry is generally composed of a number of subordinate branches, chain headquarters, and distribution centers. Industry headquarters, branches, and distribution centers are often located in different locations in a city. Their respective LAN servers need to be remotely connected via the Internet. The sales industry information management system adopts a distributed database structure: the primary data server is located in the headquarters, and the secondary data server is located in each branch. All servers constitute a distributed database system as a whole.
The block diagram of the commodity sales structure in the logistics industry is shown in Figure 1. Each sales shop consists of a payment system, a purchase system, a wireless handheld terminal, and a management system. The four systems are connected by a computer network. The core devices of the payment system, the purchase system, and the wireless handheld terminal are also RFID readers. The difference is that the payment system deletes commodity records from the database, the purchase system adds commodity records to the database, and the wireless handheld terminal serves customers and staff. use. 
2.2 System hardware design The reader/writer is an indispensable hardware device device of the radio frequency identification system. It is a tool for data exchange between the system and a large number of mobile electronic tags. It is a key part of the system operation. The technical parameters of the reader/writer are the overall performance and reliability of the system. Sex has a decisive influence. Hardware design is the key to the performance of the reader. Its goal is to achieve a long reading distance, a high recognition rate, and a 100% recognition rate. The design of a general radio frequency reader/writer is mainly composed of a control module, a radio frequency transceiver module, an antenna unit, a communication interface module, and a power supply module. After the study found that can take some measures to improve the performance of the reader. Aiming at the application characteristics of chain operation, a passive backscatter RFID reader is more suitable. Structurally, it can be divided into two parts, namely the RF front-end and the digital baseband. The RF front-end part includes the transmitting circuit, receiving circuit, circulator and antenna; the digital baseband includes DSP and FPGA chips. Among them, the transmission circuit can be subdivided into a carrier circuit, a modulation circuit, and an amplification circuit. Figure 2 shows the reader structure block diagram. 
Its working process: The carrier circuit controls the voltage controlled oscillator through the phase locked loop, produces the carrier frequency, sends to the modulation circuit; The mixer mixes the carrier signal and the reader's base band signal into the modulation signal in the modulation circuit, passes the low noise amplifier After being filtered, it is sent to the amplifier. According to the need, the reader/writer adjusts the gain of the transmitted signal through the attenuator. The transmitted signal passes through the RF power amplifier and is sent to the antenna of the reader/writer via the circulator.
2.3 System Software Design The software system uses an open source operating system with embedded operating system as its management platform, which has strong stability and security and a compact structure. In addition, the software system has also taken many security technical measures, including permission control for reading and writing, subsystems with protection, audit trails, and core authorizations, providing users with the necessary security guarantees. The radio frequency reader function and interface control function system are shown in Figure 3. 
2.4 Anti-collision algorithm The quantity of goods purchased by a customer from a sales shop (such as a supermarket) is generally large. It is necessary to accurately and completely identify these products in the shortest possible time. This is a problem that the anti-collision algorithm needs to solve. Reading multiple tags at the same time is often the place where RFID is much better than graphic code. However, if there is no anti-collision function, RFID system can read and write only one tag. In this case, if there are more than two items in the readable range at the same time, it will lead to reading errors.
The study of anti-collision problem mainly needs to solve two problems: avoid or reduce the conflict between the reader and the tag; avoid or reduce the interference between the readers. In order to reduce chain store costs and increase chain store profits, the retail industry uses passive tags. According to the EIC/ISO18000-6 standard, only TYPEB tags can be used, so anti-collision algorithms can only use binary algorithms. Binary search algorithm is the most commonly used anti-collision algorithm of RFID system. The algorithm is very flexible and anti-collision failure will not occur. For conflicting N tags, only a certain number of anti-collision cycles are required to accurately identify the appropriate tags. The basic idea of ​​this algorithm is that the reader determines the location of the data collision generated when the serial number of the tag is sent, and then forcibly orders those tags that send information “0†or “1†at the conflict location to exit the conflict. When the N-1 transponders exit the conflict, the remaining channels are completely occupied by the tag and recognized by the reader.
3. The situation that RFID faces in the sales of the logistics industry The biggest obstacle that restricts the development of RFID is the technical standards. There are currently 117 RFID protocol standards for data exchange worldwide. Excessive and excessive agreements lead to ununified terms and limit the improvement of standards in practice. At present, there is a lack of authoritative and unified standards that are globally observed. Because of the many aspects involved in RFID, the work involved in setting standards is very complicated. There are also disputes over the frequency bands used by RFID in relation to the formulation of standards. To use RFID technology to achieve information exchange in the global logistics field, there must be a global unified logistics RFID frequency band. At present, the United States uses 915 MHz, Europe uses 805.8 MHz, and Japan uses 960 MHz.
Price is still a key factor in limiting the scale of RFID development. Each foreign country has achieved 5 cents, and the domestic minimum price is 0.7 yuan each. In spite of this, for large-scale promotion, the prices of RFID tags and reading devices are still too high. The price and scale are a contradiction. Manufacturers want to reduce costs by scaling up, while more users wait for prices to drop before entering. In China, to solve the price bottleneck of RFID, the localized production of labels and reading equipment must also be resolved.
4. Conclusion In conclusion, RFID technology is one of the core competitiveness of the logistics industry's sales operations. Improving the operational efficiency of commodity logistics systems is a fundamental measure for improving the overall system response speed, an important cornerstone for sustainable corporate development, and a fundamental requirement for reducing the overall operating costs of the sales industry, improving competitiveness and profitability. The RFID technology is applied to the sales management of the logistics industry. The population is installed in the goods warehouse and the payment system is installed at the outlets of the chain stores. It is connected to the management system through the computer network. This constitutes a complete logistics industry sales system. This can effectively improve the management level and reduce operating costs.
With the acceleration of economic globalization. The demand for response speed in the supply chain continues to increase, prompting the global logistics industry to constantly explore new technologies that can improve efficiency and service quality. Modern logistics makes full use of information technology and integrates transportation, warehousing, loading and unloading, processing, finishing and distribution to form a complete supply chain. The fundamental purpose of modern logistics is to improve logistics efficiency, reduce logistics costs, meet customer needs, and increasingly show trends of information, networking, automation, functionalization, and standardization. Informatization is the core of modern logistics. RFID will play a decisive role in the informatization construction of the logistics industry.
Figure 3 RF reader function and interface control function system